Tuning Second Near-Infrared Fluorescence Activation by Regulating the Excited-State Charge Transfer Dynamics Change Ratio
Linrong Chen, Meitang Peng, Yanni Ouyang, Jian Chen, Haoze Li, Min Wu, Rui Qu, Wenya Zhou, Chunfeng Zhang, Yuyan Jiang, Shidang Xu, Wei Wu, Xiqun Jiang, Zhen Xu
Abstract
Second near-infrared (NIR-II) fluorescence imaging holds great promise for studying biopathological processes with high spatial resolution. However, developing activatable NIR-II fluorescent probes (AFPs) remains challenging due to insufficient signal activation in response to biomarkers and labor-intensive probe optimization. Here, we identify the excited-state charge transfer dynamics change ratios (δ) as a critical determinant of the fluorescence "turn-on" ratio of AFPs. We design a series of AFPs and their uncaged counterparts (uAFPs) and systematically analyze their photophysical characteristics and responsiveness. Comprehensive analyses including computational calculations, femtosecond transient absorption spectroscopy, steady-state fluorescence spectra, and fluorescence titration experiments verify a strong correlation between the theoretical and experimental δ values and the fluorescence "turn-on" ratios of activated AFPs. As a proof of concept, the optimal probe AFP2 indicated by δ enables early diagnosis of drug-induced liver injury and ultrasensitive detection of tiny metastatic foci (<2 mm) in mouse models, demonstrating superior sensitivity outperforming conventional methods. This study highlights the potential of δ as a predictor of probe responsiveness, which can streamline and accelerate the development and optimization of NIR-II AFPs for broader preclinical and translational applications.